1. Field of the Invention
The present invention relates to an oil pump in which the discharge volume is varied between low-speed rotation and high-speed rotation of rotors due to rotation of a reference line linking a center of an inner rotor and a center of an outer rotor, and in which the pump efficiency can be improved.
2. Description of the Related Art
Conventionally, there is an internal gear type of oil pump in which the pump discharge volume can be varied by rotational movement of a reference line which is a line linking the center of the inner rotor and the center of the outer rotor. Examples of this type of pump are disclosed in Domestic re-publication of PCT international application WO 2010/013625 and Japanese Patent Application Publication No. 2010-96011. Below, the oil pump disclosed in Domestic re-publication of PCT international application WO 2010/013625 and Japanese Patent Application Publication No. 2010-96011 will be described in general terms. In the description, the reference symbols employed in Domestic re-publication of PCT international application WO 2010/013625 and Japanese Patent Application Publication No. 2010-96011 are used as is without alteration.
The eccentric variable-capacity pump which is disclosed in Domestic re-publication of PCT international application WO 2010/013625 is provided with guide means G for setting an attitude of an adjusting ring 14 fitted externally onto an outer rotor 13, by causing rubbing contact of a contact section C of the adjusting ring 14 against a guide surface S of a casing 1 (see FIG. 2 in Domestic re-publication of PCT international application WO 2010/013625).
The guide means G includes a first guide pin 21 and a second guide pin 22 which pass through a first arm section C1 and a second arm section C2 formed on the adjusting ring 14, in a parallel attitude with respect to a driving rotation axis center X, and includes a circular arc-shaped first guide groove T1 and a circular arc-shaped second guide groove T2 formed in a wall section 1A of the casing 1, in accordance with the first guide pin 21 and the second guide pin 22.
The first guide groove T1 and the second guide groove T2 are formed into a shape whereby when the adjusting ring 14 moves, a driven axis Y performs an orbiting motion about the drive rotation axis center X, while at the same time the adjusting ring 14 performs a rotating motion about the idle axis center Y.
Furthermore, conventionally, there is an internal gear type oil pump in which a shallow groove is formed on a seal land which is formed between a trailing end section of a discharge port and a leading end section of an intake port. In the oil pump disclosed in Japanese Patent Application Publication No. 2010-96011, a groove 11a is provided in a small seal land so as to extend in the forward direction of rotation of the rotor from the outer diameter side of the rotor of the trailing end of the discharge port 7 (see FIG. 1 and FIG. 3 in Japanese Patent Application Publication No. 2010-96011).
Due to a liquid pressure being introduced from the groove 11a into a space g at a position where the volume of the pump chamber 10 is smallest, thereby pressing together the teeth of the outer rotor 3 and the inner rotor 2 on opposite sides half a cycle apart, the tip clearance between the rotors is compressed and the amount of liquid leakage via the tip clearance is reduced (see FIG. 4A in Japanese Patent Application Publication No. 2010-96011).
Connection between the pump chamber 10 and both the intake port 6 and the discharge port 7 needs to be shut off between the discharge finish point and the intake start point, and in order to ensure this function even when the groove 11a is provided, an escape section 12 is formed, which causes one portion of the outer circumferential side of the rotor at the leading end of the intake port 6 to be displaced in the forward direction of rotation of the rotor (see FIG. 3 in Japanese Patent Application Publication No. 2010-96011).